Path: utzoo!attcan!uunet!lll-winken!lll-lcc!ames!mailrus!ncar!tank!uxc!uxc.cso.uiuc.edu!m.cs.uiuc.edu!grogers
From: grogers@m.cs.uiuc.edu
Newsgroups: comp.windows.x
Subject: Re: Using Multiple Graphics Contexts
Message-ID: <26900057@m.cs.uiuc.edu>
Date: 20 Dec 88 03:13:00 GMT
References: <8404@pasteur.Berkeley.EDU>
Lines: 26
Nf-ID: #R:pasteur.Berkeley.EDU:8404:m.cs.uiuc.edu:26900057:000:1088
Nf-From: m.cs.uiuc.edu!grogers    Dec 19 21:13:00 1988


Within our XGKS library we found two significant speedups related to GCs.
The first was to use more of them.  At first we used one GC for all five
gks output primitives.  This meant that we were changing the color, pattern,
etc. values in the GC with just about every gks output function call.  We
later changed to using one GC per output primitive type.  Although we have
no benchmark evidence, the speedup was visually apparent for all programs.
The second speedup was to peek at the Xlib's cached GC to avoid making Xlib
calls to set GC values to what they currently are.  This again made a
noticeable difference.  This is because Xlib does not filter out unnecessary
nonchanges to the GC.

Based on our experience I would recommend using GCs to avoid GC changes and
modifying the Xlib implementation to filter out the nonchanges.


Greg Rogers
University of Illinois at Urbana-Champaign
Department of Computer Science
1304 W. Springfield Ave.
Urbana, IL 61801

(217) 333-6174

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